quick selection of a random row from a large table in mysql

Question

What is a fast way to select a random row from a large mysql table?

I\'m working in php, but I\'m interested in any solution even if it\'s in another language.

Answer 1

I'm a bit new to SQL but how about generating a random number in PHP and using

SELECT * FROM the_table WHERE primary_key >= $randNr

this doesn't solve the problem with holes in the table.

But here's a twist on lassevks suggestion:

SELECT primary_key FROM the_table

Use mysql_num_rows() in PHP create a random number based on the above result:

SELECT * FROM the_table WHERE primary_key = rand_number

On a side note just how slow is SELECT * FROM the_table:
Creating a random number based on mysql_num_rows() and then moving the data pointer to that point mysql_data_seek(). Just how slow will this be on large tables with say a million rows?